1. Field of the Invention
The present invention relates to projection systems and projection screens and more particularly to an improved screen apparatus that includes a double layered screen construction.
2. Background of the Related Art
Projected light may be used to display images on large surfaces, such as large computer displays or television screens. In a front projection system, an image beam is projected from an image source onto the front side of a reflection-type, angle transforming screen, which then reflects the light toward a viewer positioned in front of the screen. In a rear projection system, the image beam is projected onto the rear side of a transmission-type, angle transforming screen and transmitted toward a viewer located in front of the screen.
Referring to FIG. 1, wide angle projection systems that include a screen apparatus 10 are known to optimally use a conventional Fresnel lens 11 in combination with some diffusing element, such as a substrate covered with glass beads (e.g., a type of diffuser or diffusive screen) 12. The combination forms an imaging screen that produces an image. The Fresnel lens 11 and the diffuser assembly 12 are held in relatively rigid or semi-rigid spaced apart relation to assure proper operation of the combination. Such screens, known generally in the art as xe2x80x9cblack matrix beadxe2x80x9d or xe2x80x9cBMBxe2x80x9d screens, are commercially available from Minnesota Mining and Manufacturing Company and others. Fresnel lenses used in devices such as overhead projectors and projection television are commercially available from, for example, Fresnel Optics, Minnesota Mining and Manufacturing Company, and others. The Fresnel lens 11 element is constructed to provide the optical properties of a much thicker lens, however, with smaller thickness and weight. Concentric steps or discontinuities 11A allow these optical and physical properties to be realized. Each of the steps has a curved profile, in cross-section, that exhibits optical power to redirect incident light 13. The cut-out sections that define the steps reduce the overall size and weight.
In FIG. 1, the Fresnel lens 11 receives the incoming light 13 from a projection image engine or image projector 14 (e.g., a liquid crystal display imager, a light source, and a projection lens that produce image light in response to input video or other signals). The break in the light path of the light 13 shown in FIG. 1 is included to recognize that the light 13 may be processed or filtered, for example, projected by the projection or other lens (not shown), and is generally indicated by numeral 13A. The screen apparatus 10 and the image engine 14 are arranged such that a light beam exiting the Fresnel lens 11 is collimated, as shown by parallel rays of light 15. The collimated rays 15 pass across an air gap 16 to a matrix of glass beads 17-21 in the diffuser assembly 12. The glass beads 17-21 are mounted upon an adhesive black mask layer 22 that is on a first surface 23 of a substrate 24 of the diffuser assembly 12. As the collimated light rays 15 strike any of the glass beads 17-21, the rays 15 are refracted and focused to a point as shown in FIG. 1. The substrate 24 is light transparent so that a viewer 27 can see an image from the light 25 that passes through a surface 26 (e.g., an acrylic, polystyrene, other polymer, or like surface) of the screen apparatus 10. The exiting rays are now wide angle transformed for wide angle viewing. The screen apparatus 10 can be an xe2x80x9ctouch screenxe2x80x9d television screen, having a large diagonal dimension, for example, substantially 60 inches, or a computer monitor screen.
Problems have been associated with BMB-type screens that affect their manufacturing quality control. Uniformity of bead diameter has been problematic with the BMB screens of the type having beads placed directly upon a substrate. In these screens the beads are, for example, attached to the substrate by an adhesive. Some adhesives used in BMB screens define a black matrix that can have holes. These holes may allow light to pass through at improper locations. Another problem with bead placement upon a matrix is associated with packing density. Often it is difficult to insure that the beads are densely packed enough to avoid light transmission non-uniformity or image non-uniformity. The beads themselves may also suffer from diameter variations, transparency differences, and surface glare, and may include relatively large inactive portions and therefore non-useful parts.
The present invention is directed to avoid or substantially avoid some or all of the problems set forth above, as well as other problems.
The above references are incorporated by reference herein where appropriate for appropriate teachings of additional or alternative details, features and/or technical background.
An object of the invention is to solve at least the above problems and/or disadvantages and to provide at least the advantages described hereinafter.
In general, in one aspect, embodiments of the invention feature a screen apparatus that includes a first layer for substantially collimating light, a second continuous layer positioned proximate the first layer for receiving the substantially collimated light from the first layer and for converging the received substantially collimated light, and a third layer adjacent the second layer, having a plurality of openings for receiving and altering the converging light as image light. The second layer includes an array of bead-like members.
Additional advantages, objects, and features of the invention will be set forth in part in the description which follows and in part will become apparent to those having ordinary skill in the art upon examination of the following or may be learned from practice of the invention. The objects and advantages of the invention may be realized and attained as particularly pointed out in the appended claims.